International application WO 03030333 (published 4 Oct. 2003) describes an electric motor consisting of a rotor that includes two circular rows of permanent magnets and a stator that contains a circular row of separated from each other electromagnets. Each magnetic-force-conducting element of the electromagnet has two polar parts connected with a linking piece and spaced with respect to each other along the rotational axis. The winding of the electromagnet is positioned on the linking piece of the magnetic-force-conducting element.
From U.S. Pat. No. 6,727,630 (published 27 Apr. 2004) an electric motor is known which consists of a rotor that includes a circular row of permanent magnets and of a stator that contains a circular row of spaced electromagnets. Each magnetic-force-conducting element of the electromagnet has two polar parts coupled with a linking piece and separated from each other in a peripheral direction. The winding of the electromagnet is made of two coils positioned on the polar parts of the magnetic-force-conducting element.
Patent application JP 2000050610 (published 18 Feb. 2000) describes an electric motor that consists of a rotor that includes a circular row of permanents magnetic poles and a stator that contains a circular row of spaced electromagnets. Each magnetic-force-conducting element of the electromagnet has two polar parts connected with a linking piece and spaced with respect to each other in the direction peripheral with regard to the rotational axis. The winding of the electromagnet is positioned on the linking piece.
The general flaw of electric motors described in WO 03030333, U.S. Pat. No. 6,727,630 and JP 2000050610 is that the part of the winding responsible for generating the magnetomotive force and positioned between the polar parts of the magnetic-force-conducting element is less than half the length of the whole winding. This increases heat losses in the winding and makes it impossible either to increase the torque without increasing the magnetomotive force or to increase the magnetomotive force without increasing heat losses in the windings.
International application WO2006115071 (published 2 Nov. 2006) describes an electric motor that contains a rotor including a number of circularly distributed pairs of permanent magnets and a stator including a circular row of spaced electromagnets. The permanent magnets in each pair are placed next to each other so that their pole surfaces face each other with the same magnetic polarity and cross the peripheral direction. All polar surfaces of the magnetic-force-conducting element belong to one plane which is parallel to the rotational axis. The circular row of electromagnets embraces the circular row of the pairs of permanent magnets. The winding of the electromagnet is positioned upon the central polar part of the magnetic-force-conducting element. Compared to the electric motors described above, the drawback of this electric motor is low torque accompanied by high heat losses in the windings, which is accounted for by the magnetic reluctance of the gap between the polar parts and the magnetic poles. Another flaw of this design is a discrete type of rotation, the principle of which is based on the repulsion of facing each other magnetic poles from the polar surfaces of the central polar part. Besides, this electric motor cannot be manufactured so that the circular row of the pairs of the permanent magnets embraces the circular row of the electromagnets.
We chose an electric motor known from U.S. Pat. No. 6,710,502 (published 23 Mar. 2004) as a prototype. This electric motor contains a rotor including three circular rows of permanent magnets connected into a magnetic circuit and a stator including a circular row of spaced electromagnets. Each magnetic-force-conducting element of the electromagnet has a central polar part and two lateral polar parts connected with the central polar part and spaced from the opposite sides of the central polar part along the rotational axis.
The angular dimensions of the polar surfaces of the polar parts are essentially the same. The winding of the electromagnet consists of two coils, positioned on the linking pieces of the magnetic-force-conducting element.
The drawback of the existing engineering solution is placing the windings on the linking pieces of the magnetic-force-conducting element as well as the fact that the lateral polar parts are spaced from the opposite sides of the central polar part along the rotational axis. This makes it impossible to increase the torque without increasing the magnetomotive force of the windings and, accordingly, either increasing heat losses in the windings while keeping their mass the same or increasing the mass of the windings while keeping the level of heat losses the same. Moreover, in the existing engineering solution the lateral polar parts are spaced from the opposite sides of the central polar part along the rotational axis, which does not allow one to optimize magnetic fluxes in the magnetic-force-conducting element in order to increase the torque by varying the distance between the centers of the polar surfaces.